As a foam dispenser, which dispenses a content liquid contained in a dispenser body in a foamed state, there is known, for example, a pump foamer, which foams and dispenses the content liquid in response to a press of its pump head portion while the dispenser is kept stationary, without requiring user to, for example, manually stir the content liquid. In the pump foamer, a foam dispensing unit, which is configured to mix the content liquid with air to foam and dispense the content liquid, is mounted on a neck portion of a dispenser body. In the foam dispensing unit, a cap portion mounted on the neck portion of the dispenser body, for example, includes a pump mechanism including a cylinder portion in which a piston (liquid piston) for drawing, pressurizing and discharging a content liquid and another piston (air piston) for drawing, pressurizing and discharging air are concentrically arranged in series. In response to a push of the pump head portion protruding upward from the cap portion, the pistons of the pump mechanism are actuated to pressurize and discharge the content liquid and air inside the cylinder portion, and mix the content liquid and air in a confluence space, and the content liquid mixed with air is then allowed to pass through a porous member such as a mesh ring so as to foam the content liquid and dispense the foamed content liquid to the outside (see, for example, Patent Literature 1).
As another type of foam dispenser, for example, a squeeze foamer is known (see, for example, Patent Literature 2). The squeeze foamer is configured as follows: in response to a squeeze (press) of a flexible bottle-shaped dispenser body held in hand, the dispenser body deforms to decrease its volume decreases; and thereby a content liquid and air contained in the dispenser body are pumped out to a vertical dispensing flow channel of a nozzle cap including a dispensing nozzle portion constituting a foam dispensing unit, and allowed to pass through a porous member such as a mesh attached to the vertical dispensing flow channel so as to foam and dispense the content liquid through the dispensing nozzle portion.